What do the following two equations represent? $-x+y = 4$ $-4x-4y = 5$
Answer: Putting the first equation in $y = mx + b$ form gives: $-x+y = 4$ $y = x+4$ Putting the second equation in $y = mx + b$ form gives: $-4x-4y = 5$ $-4y = 4x+5$ $y = -1x - \dfrac{5}{4}$ The slopes are negative inverses of each other, so the lines are perpendicular.